1. Field of the Invention
The present invention relates generally to embolectomy and thrombectomy devices for manipulating and treating thrombus and clots in the vascular system and, more particularly, to expandable intraluminal catheters for removing occlusive materials from body passages.
2. Description of Related Art
Expanding diameter catheters are commonly used in surgical procedures. A well-known mechanism for expanding the diameter of the catheter is inflation. These balloon-type embolectomy catheters are disclosed in U.S. Pat. No. 3,435,826, U.S. Pat. No. 3,467,101, and U.S. Pat. No. 5,320,604 for use in removing blood clots and thrombus from blood vessels. In addition to balloon-type embolectomy catheters, other mechanisms have been proposed by the prior art in an attempt to improve the procedure of removing clots and thrombus or plaque from blood vessels. U.S. Pat. No. 5,282,484 and U.S. Pat. No. 5,284,486 disclose a catheter having rotating blades. U.S. Pat. No. 5,370,653 discloses a catheter having a brush for removal of material from a blood vessel. U.S. Pat. No. 5,192,290, which is assigned to the assignee of the present invention, discloses a catheter having an expanding elastomeric foam.
All of these prior art embolectomy catheters have intrinsic problems and complications connected with use in delicate blood vessels, regardless of whether balloons, blades, or brushes are used. Since a balloon must be inflated to relatively high pressure in order to ensure proper results, the balloon may rupture or transmit excessive force to the delicate blood vessel. Sclerotic lesions, for example, may occur at sites where the intimal lining of the vessel has been damaged. Blades or brushes can cause extensive damage to the fragile lining of the delicate blood vessel, as well. An elastomeric foam member, such as that disclosed in U.S. Pat. No. 5,192,290, provides a mechanical activation of the expansion means. Although this mechanical activation provides a safety measure by giving the user a tactile feel, the elastomeric foam expansion member does not have the removal capabilities of the above-mentioned balloons, blades, and brushes.
Another problem commonly shared by all of the prior art embolectomy catheters stems from a removal method which is inherently engineered into these devices. A common principle is implemented by each of the prior art devices. Specifically, the expanding members of these prior art devices are advanced beyond the occlusive material to be removed or treated in the blood vessel, and the occlusive material is then forced as a whole along a retrieval path through the blood vessel to a collection site. If the occlusive material is well-attached to the blood vessel wall, the shear forces required to dislodge this material may be damaging to the blood vessel. Since the expanding member basically contacts a perimeter portion of the occlusive material and pushes this material through the vessel to the collection site, a resulting compression of the occlusive material often results. This compression may necessitate the application of additional, excessive force for the removal of the occlusive material, resulting in further damage to the delicate intimal lining of the blood vessel.